When Russia struck Ukraine with a nuclear-capable intermediate range ballistic missile, armed with multiple conventional independent re-entry vehicles, it was a clear instance of signaling by Moscow.

And what was that message that Moscow? That Vladimir Putin may for the first time be ready to use nuclear weapons following the White House’s recent lifting of employment restrictions on U.S.-provided ATACMS missiles to Ukraine.

While we at the Heritage Foundation condemn this strike on Ukraine, we must understand the seriousness of the situation.

This November, the Biden Administration lifted range restrictions on the employment of U.S.-provide ATACMS to Ukraine. The Administration argued that this was done in response to the deployment of North Korean combat forces in Ukraine—but oddly, that it would not be a game changer on the battlefield. U.S. Secretary of Defense Lloyd Austin went so far as to say: “I don’t believe one capability is going to be decisive.”

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Beginning with the February 2022 invasion of Ukraine, the Biden Administration, step by step, gave more weapons to Ukraine—to include artillery and small arms, tanks, armored personnel carriers, air and missile defenses, eventually to include longer and more accurate missiles. Throughout this period, the Biden Administration restricted the employment of American-provided weapons to only attacking Russian forces inside of Ukraine.

Each time Washington provided new weapons to Ukraine, Russia would issue new nuclear threats to Ukraine, NATO members—and the United States. Indeed, in the fall of 2022 and the summer of 2023, there were real concerns in Washington that Russia might actually use nuclear weapons on the battlefield. However, as time passed and this failed to materialize, many defense analysts in the West believed that Vladimir Putin was becoming the Boy Who Cried Wolf—and dismissed the seemingly never-ending series of nuclear threats.

Following the White House’s lifting of restrictions on the American-supplied ATACMS missiles, Ukraine launched ATACMS at targets inside of Russia itself. Almost immediately, Moscow began to issue a new round of nuclear threats—but these were qualitatively different from all that came before.

Within days, Russia released an updated nuclear employment doctrine which stated that Moscow would view an attack against Russia by a non-nuclear power with the “participation or support of a nuclear power” as a “joint attack on the Russian Federation.” The new nuclear doctrine also noted that Russia would view aggression against Russia by a member of a military alliance as “an aggression by the entire bloc,” a clear reference to NATO. It also asserted that Russia could use nuclear weapons in response to a massive air attack of ballistic and cruise missiles, aircraft, or drones.

Following the release of the new nuclear employment doctrine, Russian Foreign Minister Sergey Lavrov stated publicly that Russia did not want a war with the West or see nuclear weapons employed in combat, but that Washington was making such an outcome more likely through its actions.

What has changed is the nature of the Russian attack on Ukraine with a nuclear-capable intermediate range ballistic missile. While it is unclear what the specific missile was, many suggest that it was a variant of an RS-26, a Russian intermediate to intercontinental range ballistic missile designed to put multiple independent nuclear reentry vehicles onto a target.

To carry out such an attack, Russia may have had to remove nuclear warheads from the missile, replace them with multiple independent conventional warheads, and then launch—almost certainly, the first time such a thing has happened. Even during the worst days of the Cold War, the United States and the Soviet Union did not strike each other’s allies or partners with conventional warheads carried by nuclear-capable ballistic missiles as part of a signaling campaign.

Given that the attack fortunately had limited operational effect—it did accurately simulate a nuclear strike in the way it was launched from long-distance, followed a ballistic trajectory, and then showered its intended target with multiple independent warheads. In the Cold War, the White House and the Pentagon would have been staffed with defense strategists who understood such messages and signaling. Thirty-three years after the dissolution of the Soviet Union, it is far from clear if such strategists are resident at the highest levels of government to even understand the message being sent.

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While such an attack could of course be yet another bluff, it is plausible that Moscow ordered the attack as a signal to Washington that it has gone too far in supporting Ukraine and that strikes on Russian soil with American made weapons are unacceptable—and that the next time, a ballistic missile might be armed with something other than conventional warheads.

Indeed, it is reasonable to assume that Moscow is trying to signal very clearly, directly, and openly that the United States has crossed a redline and that Moscow is now approaching the point where it will employ nuclear weapons on the battlefield in Ukraine.

Moscow may still be crying wolf. But in the children’s tale, the very act of repeatedly crying wolf meant that no one knew when the cry was true. Given that Russia has roughly 10 times as many operationally deployed tactical nuclear weapons as the United States does, Washington must at a minimum consider that this time, Russia is serious about employing nuclear weapons on the battlefield.

While the Heritage Foundation has and continues to wish Ukraine success in its fight for independence from Russia, President Biden’s lifting of restrictions on Ukrainian employment of American-supplied missiles is needlessly reckless. President Biden—or failing that, President-elect Trump—should reimpose sensible restrictions on the employment of U.S. weapons and seek an end to this war. Failure to do so imposes unacceptable levels of risk on the American people and American national security—with no real benefit to the United States.

Put simply, it is not in American interests to risk even a limited nuclear war with Russia over Ukraine.